Label-independent-detection (LID)-based optical readers can be used, for example, to detect drug binding to a target molecule such as a protein, or changes in living cells as material is displaced within a cell in response to a drug. Certain types of LID optical readers measure changes in refractive index on the surface of a resonant waveguide grating (RWG) biosensor for an array of RWG biosensors. The individual RWG biosensors are located in respective wells of a microplate.
One type of LID optical reader employs a narrowband light source, wherein narrow-band light (i.e., on the order of the resonance reflectance linewidth of the RWG biosensor) is directed to each RWG biosensor using a narrow-band tunable light source. The interrogation light is swept over a range of wavelengths to determine the center resonance wavelength of the RWG biosensors. However, alternative approaches where the RWG biosensors are illuminated with broadband light are desirable.